Effects of Wet and Dry Micronization on the GC-MS Identification of the Phenolic Compounds and Antioxidant Properties of Freeze-Dried Spinach Leaves and Stems

Abstract

Micronization is an emerging technology used in food production, in which the size of particles is reduced to microns in the processing of plant raw materials and by-products, thus making it an interesting research topic. Spinach stems are by-products of spinach leaf processing, but there is little information regarding their processing and possible reuse. In this study, wet and dry ball mill micronization, in combination with freeze drying, was used to process spinach stems and leaves to obtain functional powders. The color and particle size of the micronized spinach leaf and stem powders were evaluated. The antioxidant activity (AA) of the powders and phenolic compounds present in them were determined using GC-MS analysis. The results obtained showed that the dry micronization of leaves and stems resulted in smoother and brighter powders than wet micronization. Significantly smaller particle sizes were achieved using the dry micronization of the leaves and stems (Dv50 = 19.5 and 10.1 µm, respectively) rather than wet micronization (Dv50 = 84.6 and 112.5 µm, respectively). More phenolic compounds, such as o-coumaric acid and gallic acid, were extracted from the dry-micronized powders. The dry micronization of the stems significantly increased the total phenolic content, and the AA of these powders was also increased. These findings demonstrate that spinach leaves and stems subjected to dry micronization can be valuable functional components of food.

Micronized Powder of Raspberry Pomace as a Source of Bioactive Compounds

“…For the longest time (20 MRP), the share of red color a* was highest in the micronized samples, and the share of yellow color b* was highest in the micronized samples (20 MRP). Previous research [ 28 ] has shown that the micronization method affects the color of spinach stems and leaves. In comparison to the control sample and dry micronization, wet micronization produced a darker color.…”

“…The content of the other phenolic compounds was not significantly different for all samples tested. In our previous studies [ 28 ] on wet and dry micronization of spinach leaves and stems, it was observed that both dry and wet micronization affected the contents of o-coumaric acid and gallic acid. In addition, dry micronization of spinach leaves increased the content of 3-hydroxyphenylacetic acid, 4-hydroxyphenylacetic acid, and p-coumaric acid.…”

“…Analyses of the particle size of control raspberry pomace powder (CRP) and micronized raspberry powders (10 and 20 MRP) were performed on a Mastersizer 3000 (Malvern Instruments Ltd., Malvern, UK) [ 28 , 52 ]. Measurements were made using a dry dispersion adapter (Aero S).…”

“…This technology has developed rapidly in food production in recent decades [ 25 , 26 , 27 ]. Previous research has proven that the micronization process can be applied to plant materials, resulting in increased functionality [ 28 , 29 ].…”

The Influence of Micronization on the Properties of Black Cumin Pressing Waste Material

“…There are several micronization methods, including fine grinding in a ball mill. The efficacy of a ball mill in lowering the particle sizes of various plant materials has been demonstrated [ 11 , 12 ]. A previous study on grape pomace powders demonstrated that grinding these materials boosted the powders’ solubility while decreasing their ability to retain water and bind oil and cations.…”